Actuation mechanism for use with an ultrasonic surgical instrument

ABSTRACT

An ultrasonic clamp coagulator assembly that is configured to permit selective cutting, coagulation and clamping of tissue during surgical procedures. An elongated portion of the instrument can be configured for endoscopic applications and has an outside diameter of less than 6 mm. The construction includes a clamping mechanism, including a clamp arm pivotally mounted at the distal portion of the instrument, which is specifically configured to create a desired level of tissue clamping forces, exceeding 4 pounds when the trigger is fully closed. The clamping mechanism includes a force-limiting mechanism that effectively smoothes out abusive tissue forces.

REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/269,546, filed on May 5, 2014, now U.S. Pat. No. 9,901,359,which is a divisional of U.S. patent application Ser. No. 12/761,431,filed on Apr. 16, 2010, now U.S. Pat. No. 8,715,306, which is adivisional of U.S. patent application Ser. No. 12/468,130, filed on May19, 2009, which is a continuation of U.S. Pat. No. 7,544,200, whichclaims the priority benefit of U.S. provisional patent application Ser.No. 60/617,427, filed on Oct. 8, 2004, and 60/676,709, filed on May 2,2005, all of which are incorporated herein by reference.

This application contains subject matter that relates to andincorporates by reference in their entirety, for any and all purposes,the following non-provisional applications:

TISSUE PAD FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser. No. Ser.No. 11/245,819, abandoned;

COMBINATION TISSUE PAD FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT,Ser. No. 11/246,794, filed Oct. 7, 2005, now U.S. Pat. No. 7,544,200;

ACTUATION MECHANISM FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser.No. 11/246,826, filed Oct. 7, 2005, abandoned;

CLAMP MECHANISM FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser. No.11/246,264, filed Oct. 7, 2005, now U.S. Pat. No. 8,057,467;

FEEDBACK MECHANISM FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser.No. 11/246,384, filed Oct. 7, 2005, abandoned;

HANDLE ASSEMBLY HAVING HAND ACTIVATION FOR USE WITH AN ULTRASONICSURGICAL INSTRUMENT, Ser. No. 11/246,330, filed Oct. 7, 2005, now U.S.Pat. No. 7,846,155;

ULTRASONIC SURGICAL SHEARS AND TISSUE PAD FOR SAME, Ser. No. 11/065,378,filed Feb. 24, 2005, abandoned; and

HAND ACTIVATED ULTRASONIC INSTRUMENT, Ser. No. 10/869,351, filed Jun.16, 2004.

FIELD OF THE INVENTION

The present invention relates, in general, to ultrasonic surgicalinstruments and, more particularly, to an ultrasonic surgical clampcoagulator apparatus particularly configured to provide increased tissuetransaction forces.

BACKGROUND OF THE INVENTION

Ultrasonic surgical instruments are finding increasingly widespreadapplications in surgical procedures by virtue of the unique performancecharacteristics of such instruments. Depending upon specific instrumentconfigurations and operational parameters, ultrasonic surgicalinstruments can provide substantially simultaneous cutting of tissue andhomeostasis by coagulation, desirably minimizing patient trauma. Thecutting action is typically effected by an end-effector at the distalend of the instrument, which transmits ultrasonic energy to tissuebrought into contact with the end-effector. Ultrasonic instruments ofthis nature can be configured for open surgical use, laparoscopic orendoscopic surgical procedures including robotic-assisted procedures.

Ultrasonic surgical instruments have been developed that include a clampmechanism to press tissue against the blade of the end-effector in orderto couple ultrasonic energy to the tissue of a patient. Such anarrangement (sometimes referred to as a clamp coagulator shears or anultrasonic transector) is disclosed in U.S. Pat. Nos. 5,322,055;5,873,873 and 6,325,811, all of which are incorporated herein byreference. The surgeon activates the clamp arm to press the clamp padagainst the blade by squeezing on the handgrip or handle.

Some current ultrasonic shears devices, however, have the tendency tocreate tissue tags. Tissue tags are the tissue that remains clamped inthe jaw that is not transected after the majority of the tissue in thejaw has been transected and falls away. Tissue tags may result frominsufficient end-effector proximal loading and/or lower proximal bladeactivity. Surgeons may mitigate tissue tags either through the additionof vertical tension (i.e. putting tension on the tissue using the blade)or rearward traction on the device in order to move the untransectedtissue to a more active portion of the blade to complete the cut.

Some current ultrasonic shears devices utilize tissue pads that close inparallel with the surface of the blade. This presents certain problemsin terms of the pressure profile exerted on the tissue. As tissue iscompressed between the jaw and the blade, the proximal portion of theblade deflects under load more than the proximal portion of the clamparm moves in applying the load against the blade. This deflection is inpart created by the portion of the blade distal to the most distal nodeof the device. It is also partly created by the deflection of thetransmission rod proximal to the most distal node. Additionally, thefact that blade amplitude decreases moving proximal of the tip of theblade makes the situation worse since the amount of energy transferredto the tissue, even if the pressure was constant, is reduced.

Current tissue pad designs utilize PTFE material to contact the tissueand blade. Although these designs have been adequate, they tend tosuffer from longevity issues since the pads tend to deteriorate overlong surgical procedures. Additionally, newer designs of clampcoagulator shears increase blade amplitude and/or the loading of the padagainst the tissue and blade and overwhelm the pad material, resultingin less than required tissue pad life. The pad material limits theamount of force that may be applied against the tissue and blade, whichin turn limits the tissue thickness or vessel size that some currentclamp coagulator shears may effectively cut and coagulate.

Some current designs of clamp coagulator shears utilize an inner tubewithin an outer tube concept to drive the clamp arm open and close.During surgical procedures the clamp arm may be subjected to axial clampforces exceeding 2.5 pounds and/or torsional abuse loads and may causethe clamp arm to disengage from the inner tube or completely from theshears.

Some current designs of clamp coagulator shears utilize a constant forcespring mechanism that prevents the application of too much force to theclamp arm and blade. Although the mechanism provides relatively constantforce to the system, the spring imparts some slope to the force curve.In applications where the clamp force is low, the slope is notsignificant. In applications with high clamp forces, however, thedifference in force attributable to the slope over the possible range ofspring compressions becomes very significant and may exceed the maximumforce allowable in the blade, in the tube assemblies or in othercomponents of the system. The high slope could allow the maximum forceto be exceeded under abuse modes or through normal manufacturingtolerance variations. If this occurs the blade may bend, the actuationmechanism may fail or undesirable tissue effects may occur (i.e. fastcutting, but minimal tissue coagulation). This situation is aggravatedby the fact that the jaw (the clamp arm and pad) of the device can meetsufficient resistance to engage the force limiting mechanism when thejaw almost contacts the blade (when transecting thin tissue or at theend of the transaction or clamping solid objects such as other devices)or when the jaw is still open (when transecting thick tissue).

Some current designs of clamp coagulator shears utilize force-limitingsprings to ensure that clamp forces are within a specified range. It isalso necessary for the force-limiting spring design to allow the surgeonto “feather” (apply less than the maximum force and slowly increase tothe maximum force). In these mechanisms, therefore, the jaws close untila predetermined force is met and then the additional stroke drives themechanism into the force limiting range. In some cases, though, thesurgeon may, unknowingly, fail to apply the full force of the jawagainst the tissue resulting in incomplete tissue cuts or insufficientcoagulation. Alternatively, the surgeon may unknowingly release fullforce of the jaw against the tissue during a transaction that results inincomplete tissue cuts or insufficient coagulation.

Some current designs of clamp coagulator shears utilize a foot pedal toenergize the surgical instrument. The surgeon operates the foot pedalwhile simultaneously applying pressure to the handle to press tissuebetween the jaw and blade to activate a generator that provides energythat is transmitted to the cutting blade for cutting and coagulatingtissue. Key drawbacks with this type of instrument activation includethe loss of focus on the surgical field while the surgeon searches forthe foot pedal, the foot pedal getting in the way of the surgeon'smovement during a procedure and surgeon leg fatigue during long cases.

Some current designs of clamp coagulator shears have eliminated the footpedal and provided hand activation on a stationary trigger. This may becumbersome, especially for surgeons with large hands.

Some current designs of clamp coagulator utilize handles that are eitherof a pistol or scissors grips design. The scissor grip designs may haveone thumb or finger grip that is immovable and fixed to the housing andone movable thumb or finger grip. This type of grip may not be entirelyfamiliar to surgeons who use other open-type surgical instruments, suchas hemostats, where both thumb and finger grips move in opposition toone another.

It would be desirable to provide an ultrasonic surgical instrument thatovercomes some of the deficiencies of current instruments. Theultrasonic surgical instrument described herein overcomes thosedeficiencies.

BRIEF SUMMARY OF THE INVENTION

An ultrasonic clamp coagulator assembly embodying the principles of thepresent invention is configured to permit selective cutting, coagulationand clamping of tissue during surgical procedures. An elongated portionof the instrument can be configured for endoscopic applications and hasan outside diameter of less than 6 mm. The construction includes aclamping mechanism, including a clamp arm pivotally mounted at thedistal portion of the instrument, which is specifically configured tocreate a desired level of tissue clamping forces, exceeding 4 poundswhen the trigger is fully closed, notwithstanding the relatively smallcross-section of the elongated portion.

The clamping mechanism also includes a pad design and pad material thatenables the higher tissue clamping forces.

The clamp coagulator device also includes a force-limiting mechanismthat effectively smoothes out abusive tissue forces.

The clamp coagulator device also features hand activation configured insuch a way to provide an ergonomically pleasing grip and operation forthe surgeon. Hand switches are be placed in the range of the naturalswing of the surgeon's thumb, whether gripping surgical instrumentright-handed or left handed.

BRIEF DESCRIPTION OF THE FIGURES

The novel features of the invention are set forth with particularity inthe appended claims. The invention itself, however, both as toorganization and methods of operation, may best be understood byreference to the following description, taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a perspective view illustrating an embodiment of an ultrasonicsurgical instrument in accordance with the present invention;

FIG. 2 is a perspective assembly view of an embodiment of an ultrasonicsurgical instrument in accordance with the present invention;

FIG. 3a is a perspective assembly view of the clamp arm and tissue pads;

FIG. 3b is an elevation section view of the clamp arm and “T” groove;

FIG. 3c is an elevation section view of the clamp arm and dovetailgroove;

FIG. 3d is a perspective view of the tissue pads aligned and stakedwithin the clamp arm;

FIG. 3e is an elevation view of the clamp arm illustrating the taperedprofile;

FIG. 3f is a top plan view of the clamp arm;

FIG. 4a is a perspective assembly view of the blade, clamp arm, tissuepads and actuator tube with the clamp arm in the closed position;

FIG. 4b is a perspective assembly view of the blade, clamp arm, tissuepads and actuator tube with the clamp arm in the open position;

FIG. 4c is a schematic of a clamp arm in accordance with the presentinvention illustrating force calculations;

FIG. 5 is a cutaway elevation view of the housing portion of anultrasonic surgical instrument in accordance with an embodiment of thepresent invention illustrating force-limiting springs and clamp closuredetent mechanism and partial cutaway elevation view of the transmissionrod and end effector;

FIG. 6a is an exploded view of the housing illustrating the thumbactuation buttons and switch assembly and linkage of the finger gripclamp actuator;

FIG. 6b is an exploded view of the housing with the switch assemblyremoved for clarity;

FIG. 7 is a perspective assembly view of the switch assembly andelectrical ring contactors;

FIG. 8a is a perspective assembly view of the switch assembly andelectrical ring contactors;

FIG. 8b is a perspective view of the proximal end of the transducerillustrating conductor rings;

FIG. 8c is an electrical schematic of the pushbutton circuit;

FIG. 9 is a perspective view of an ultrasonic surgical instrument with acut away view of the housing and connected to a transducer;

FIG. 10 is a perspective view of an ultrasonic surgical instrument withthe trigger extended distally and the clamp arm in the open position;

FIG. 11 is a perspective view of an ultrasonic surgical instrument withthe trigger retracted proximally and the clamp arm in the closedposition;

FIG. 12 is an elevation view of a left-handed grip of an embodiment ofan ultrasonic surgical instrument in accordance with the presentinvention;

FIG. 13 is an elevation view of a left-handed grip of an ultrasonicsurgical instrument in accordance with an embodiment of the presentinvention with the index finger accessing the rotation wheel;

FIG. 14 is an elevation view of a left-handed grip of an ultrasonicsurgical instrument in accordance with the present invention with thethumb accessing a first activation button;

FIG. 15 is an elevation view of a left-handed grip of an ultrasonicsurgical instrument in accordance with the present invention with thethumb accessing a second activation button;

FIG. 16a-c are force curves illustrating various forces as a function ofthe trigger position and tissue conditions;

FIG. 17 is an elevation view of the surgical instrument with graphicalillustrations of the surgeon finger placement;

FIG. 18 is a perspective assembly view of a second embodiment of anultrasonic surgical instrument in accordance with the present invention;

FIG. 19 is an exploded view of a handpiece connector;

FIGS. 20a-b are exploded views of a large slip ring and a small slipring, respectively;

FIG. 21 is an exploded view of the flex circuit apparatus

FIG. 22 is an electrical schematic of the flex circuit of FIG. 21

FIG. 23 is an elevation view of a surgical instrument in accordance withone aspect of the invention; and

FIG. 24 is a perspective view of a surgical instrument in an alternateaspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Before explaining the present invention in detail, it should be notedthat the invention is not limited in its application or use to thedetails of construction and arrangement of parts illustrated in theaccompanying drawings and description. The illustrative embodiments ofthe invention may be implemented or incorporated in other embodiments,variations and modifications, and may be practiced or carried out invarious ways. Further, unless otherwise indicated, the terms andexpressions employed herein have been chosen for the purpose ofdescribing the illustrative embodiments of the present invention for theconvenience of the reader and are not for the purpose of limiting theinvention.

Further, it is understood that any one or more of thefollowing-described embodiments, expressions of embodiments, examples,etc. can be combined with any one or more of the otherfollowing-described embodiments, expressions of embodiments, examples,etc.

The present invention is particularly directed to an improved ultrasonicsurgical clamp coagulator apparatus which is configured for effectingtissue cutting, coagulation, and/or clamping during surgical procedures.The present apparatus can be readily configured for use in open surgicalprocedures, as well as laparoscopic or endoscopic procedures androbot-assisted surgical procedures. Versatile use is facilitated byselective use of ultrasonic energy. When ultrasonic components of theapparatus are inactive, tissue can be readily gripped and manipulated,as desired, without tissue cutting or damage. When the ultrasoniccomponents are activated, the apparatus permits tissue to be gripped forcoupling with the ultrasonic energy to effect tissue coagulation, withapplication of increased pressure efficiently effecting tissue cuttingand coagulation. If desired, ultrasonic energy can be applied to tissuewithout use of the clamping mechanism of the apparatus by appropriatemanipulation of the ultrasonic blade.

As will become apparent from the following description, the presentclamp coagulator apparatus is particularly configured for disposable useby virtue of its straightforward construction. As such, it iscontemplated that the apparatus be used in association with anultrasonic generator unit of a surgical system, whereby ultrasonicenergy from the generator unit provides the desired ultrasonic actuationfor the present clamp coagulator apparatus. It will be appreciated thata clamp coagulator apparatus embodying the principles of the presentinvention can be configured for non-disposable or multiple use, andnon-detachably integrated with an associated ultrasonic generator unit.However, detachable connection of the present clamp coagulator apparatuswith an associated ultrasonic generator unit is presently preferred forsingle-patient use of the apparatus.

The present invention will be described in combination with anultrasonic instrument as described herein. Such description is exemplaryonly, and is not intended to limit the scope and applications of theinvention. For example, the invention is useful in combination with amultitude of ultrasonic instruments including those described in, forexample, U.S. Pat. Nos. 5,938,633; 5,935,144; 5,944,737; 5,322,055,5,630,420; and 5,449,370.

With reference to FIGS. 1-3, an embodiment of a surgical system 19,including an ultrasonic surgical instrument 100 in accordance with thepresent invention is illustrated. The surgical system 19 includes anultrasonic generator 30 connected to an ultrasonic transducer 50 viacable 22, and an ultrasonic surgical instrument 100. It will be notedthat, in some applications, the ultrasonic transducer 50 is referred toas a “hand piece assembly” because the surgical instrument of thesurgical system 19 is configured such that a surgeon may grasp andmanipulate the ultrasonic transducer 50 during various procedures andoperations. A suitable generator is the GEN 300 sold by EthiconEndo-Surgery, Inc. of Cincinnati, Ohio.

The ultrasonic surgical instrument 100 includes a multi-piece handleassembly 68 adapted to isolate the operator from the vibrations of theacoustic assembly contained within transducer 50. The handle assembly 68can be shaped to be held by a user in a conventional manner, but it iscontemplated that the present ultrasonic surgical instrument 100principally be grasped and manipulated by a trigger-like arrangementprovided by a handle assembly of the instrument, as will be described.While multi-piece handle assembly 68 is illustrated, the handle assembly68 may comprise a single or unitary component. The proximal end of theultrasonic surgical instrument 100 receives and is fitted to the distalend of the ultrasonic transducer 50 by insertion of the transducer intothe handle assembly 68. The ultrasonic surgical instrument 100 may beattached to and removed from the ultrasonic transducer 50 as a unit. Theultrasonic surgical instrument 100 may include a handle assembly 68,comprising mating housing portion 69, housing portion 70, and atransmission assembly 71. When the present instrument is configured forendoscopic use, the construction can be dimensioned such thattransmission assembly 71 has an outside diameter of approximately 5.5mm. The elongated transmission assembly 71 of the ultrasonic surgicalinstrument 100 extends orthogonally from the instrument handle assembly68. The transmission assembly 71 can be selectively rotated with respectto the handle assembly 68 as further described below. The handleassembly 68 may be constructed from a durable plastic, such aspolycarbonate or a liquid crystal polymer. It is also contemplated thatthe handle assembly 68 may alternatively be made from a variety ofmaterials including other plastics, ceramics or metals.

The transmission assembly 71 may include an outer tubular member orouter sheath 72, an inner tubular actuating member 76, a waveguide 80and end-effector 81 (blade 79, clamp arm 56 and one or more clamp pads58). As will be described, the outer sheath 72, the actuating member 76,and the waveguide or transmission rod 80 may be joined together forrotation as a unit (together with ultrasonic transducer 50) relative tohandle assembly 68. The waveguide 80, which is adapted to transmitultrasonic energy from transducer 50 to blade 79 may be flexible,semi-flexible or rigid. The waveguide 80 may also be configured toamplify the mechanical vibrations transmitted through the waveguide 80to the blade 79 as is well known in the art. The waveguide 80 mayfurther have features to control the gain of the longitudinal vibrationalong the waveguide 80 and features to tune the waveguide 80 to theresonant frequency of the system. In particular, waveguide 80 may haveany suitable cross-sectional dimension. For example, the waveguide 80may have a substantially uniform cross-section or the waveguide 80 maybe tapered at various sections or may be tapered along its entirelength. In one expression of the current embodiment, the waveguidediameter is about 0.113 inches nominal to minimize the amount ofdeflection at the blade 79 so that gapping in the proximal portion ofthe end effector 81 is minimized.

Ultrasonic waveguide 80 may further include at least one radial hole oraperture 66 extending there through, substantially perpendicular to thelongitudinal axis of the waveguide 80. The aperture 66, which may bepositioned at a node, is configured to receive a connector pin 27 whichconnects the waveguide 80, to the tubular actuating member 76, and thetubular outer sheath 72, a rotation knob 29 together for conjointrotation, including the end effector 81, relative to instrument handleassembly 68.

In one embodiment of the present invention, the ultrasonic waveguide 80may have a plurality of grooves or notches (not shown) formed in itsouter circumference. The grooves may be located at nodes of thewaveguide 80 to act as alignment indicators for the installation of adamping sheath 62 and stabilizing silicone rings or compliant supportsduring manufacturing. A seal 67 may be provided at the distal-most node,nearest the end-effector 81, to abate passage of tissue, blood, andother material in the region between the waveguide 80 and actuatingmember 76.

The blade 79 may be integral with the waveguide 80 and formed as asingle unit. In an alternate expression of the current embodiment, blade79 may be connected by a threaded connection, a welded joint, or othercoupling mechanisms. The distal end of the blade 79 is disposed near ananti-node in order to tune the acoustic assembly to a preferred resonantfrequency fo when the acoustic assembly is not loaded by tissue. Whenultrasonic transducer 50 is energized, the distal end of blade 79 isconfigured to move longitudinally in the range of, for example,approximately 10 to 500 microns peak-to-peak, and preferably in therange of about 20 to about 200 microns at a predetermined vibrationalfrequency fo of, for example, 55,500 Hz.

In accordance with the illustrated embodiment, blade 79 is curved alongwith the associated clamp arm 56. This is illustrative only, and blade79 and a corresponding clamp arm 56 may be of any shape as is known tothe skilled artisan.

Ultrasonic transducer 50, and an ultrasonic waveguide 80 togetherprovide an acoustic assembly of the present surgical system 19, with theacoustic assembly providing ultrasonic energy for surgical procedureswhen powered by generator 30. The acoustic assembly of surgicalinstrument 100 generally includes a first acoustic portion and a secondacoustic portion. In the present embodiment, the first acoustic portioncomprises the ultrasonically active portions of ultrasonic transducer50, and the second acoustic portion comprises the ultrasonically activeportions of transmission assembly 71. Further, in the presentembodiment, the distal end of the first acoustic portion is operativelycoupled to the proximal end of the second acoustic portion by, forexample, a threaded connection.

With particular reference to FIGS. 2, and 9-11, reciprocal movement ofactuating member 76 drives the clamp arm open and closed. Aforce-limiting mechanism 91 is operatively connected to actuating member76 and comprises a tube collar cap 98 that secures distal washer 97,distal wave spring 96, proximal washer 95 and proximal wave spring 94onto collar cap 93. Collar 93 includes axially extending lugs 92 inengagement with suitable openings 75 in the proximal portion of tubularactuating member 76. A circumferential groove 74 on the actuating member76 receives on O-ring 73 for engagement with the inside surface of outersheath 72.

Rotation of the actuating member 76 together with tubular outer sheath72 and inner waveguide 80 is provided by a connector pin 27 extendingthrough these components and rotation knob 29. Tubular actuating member76 includes an elongated slot 31 through which the connector pin 27extends to accommodate reciprocal movement of the actuating member 76relative to the outer sheath 72 and inner waveguide 80.

The force limiting mechanism 91 provides a portion of the clamp drivemechanism of the instrument 100, which affects pivotal movement of theclamp arm 56 by reciprocation of actuating member 76. The clamp drivemechanism further includes a drive yoke 33 which is operativelyconnected with an operating trigger 34 of the instrument, with theoperating trigger 34 thus interconnected with the reciprocable actuatingmember 76 via drive yoke 33 and force limiting mechanism 91. Trigger 34is rotatably connected to drive yoke 33 via pins 35 and 36 and link 37and rotatably connected to drive yoke 33 and housing 68 via post 38.

Movement of trigger 34 toward handgrip 68 translates actuating member 76proximally, thereby pivoting clamp arm 56 toward blade 79. Thetrigger-like action provided by trigger 34 and cooperating handgrip 68facilitates convenient and efficient manipulation and positioning of theinstrument, and operation of the clamping mechanism at the distalportion of the instrument whereby tissue is efficiently urged againstthe blade 79. Movement of trigger 34 away from handgrip 68 translatesactuating member 76 distally, thereby pivoting clamp arm 56 away fromblade 79.

With particular reference to FIGS. 1-4, therein is illustrated oneembodiment of clamp member 60 for use with the present ultrasonicsurgical instrument 100 and which is configured for cooperative actionwith blade 79. The clamp member 60 in combination with blade 79 iscommonly referred to as the end effector 81, and the clamp member 60 isalso commonly referred to as the jaw. The clamp member 60 includes apivotally movable clamp arm 56, which is connected to the distal end ofouter sheath 72 and actuation member 76, in combination with a tissueengaging pad or clamp pad 58. In one expression of the embodiment, clamppad 58 is formed from TEFLON® trademark name of E. I. Du Pont de Nemoursand Company, a low coefficient of friction polymer material, or anyother suitable low-friction material. Clamp pad 58 mounts on the clamparm 56 for cooperation with blade 79, with pivotal movement of the clamparm 56 positioning the clamp pad in substantially parallel relationshipto, and in contact with, blade 79, thereby defining a tissue treatmentregion. By this construction, tissue is grasped between clamp pad 58 andblade 79. As illustrated, clamp pad 58 may be provided with non-smoothsurface, such as a saw tooth-like configuration to enhance the grippingof tissue in cooperation with the blade 79. The saw tooth-likeconfiguration, or teeth, provide traction against the movement of theblade. The teeth also provide counter traction to the blade and clampingmovement. As would be appreciated by one skilled in the art, the sawtooth-like configuration is just one example of many tissue engagingsurfaces to prevent movement of the tissue relative to the movement ofthe blade 79. Other illustrative examples include bumps, criss-crosspatterns, tread patterns, a bead or sand blasted surface, etc.

With particular reference to FIG. 3a , a first expression of the currentembodiment includes a clamp pad 58 having a proximal portion 58 b thatis smoother than a distal portion 58 a, such that proximal portion 58 bmay be devoid of saw-tooth-like teeth or other tissue engaging surfacescontemplated. Utilizing a smooth proximal portion 58 b on clamp pad 58allows tissue in the proximal region to move distally, following thevibratory motion of the blade, to the more active region of the blade 79to prevent tissue tagging. This concept takes advantage of the inherentmotion profile of blade 79. Due to sinusoidal motion, the greatestdisplacement or amplitude of motion is located at the most distalportion of blade 79, while the proximal portion of the tissue treatmentregion is on the order of 50% of the distal tip amplitude. Duringoperation, the tissue in the proximal region of end effector (area ofportion 58 b) will desiccate and thin, and the distal portion of endeffector 81 will transect tissue in that distal region, thereby allowingthe desiccated and thin tissue within the proximal region to slidedistally into the more active region of end effector 81 to complete thetissue transaction.

In a second expression of the current embodiment, clamp pad 58 consistsof one single pad having a smooth proximal end 58 b and a distal portion58 a that comprises a saw tooth-like configuration. In a thirdexpression of the current embodiment, clamp pad 58 may consist of twoseparate components, distal portion 58 a′ that comprises saw tooth-liketeeth and proximal portion 58 b′ that is smoother relative to distalportion 58 a′. The advantage of two separate components 58 a′ and 58 b′is that each pad may be constructed from different materials. Forexample, having a two-piece tissue pad allows the use of a verylubricious material at the distal end that is not particularly resistantto high temperatures compared to a very high temperature material at theproximal end that is not particularly lubricious because the proximalend is an area of lower amplitude. Such a configuration matches thetissue pad materials to the amplitude of the blade 79.

In a fourth expression of the current embodiment of the presentinvention, clamp pad 58 a′ is formed from TEFLON® or any other suitablelow-friction material. Clamp pad 58 b′ is formed from a base materialand at least one filler material, which is a different material from thebase material. The surface of proximal clamp pad 58 b′ may be smootherthan distal clamp pad 58 a′, or proximal clamp pad 58 b′ may also have asimilar type saw-tooth configuration.

Several benefits and advantages are obtained from one or more of theexpressions of the invention. Having a tissue pad with a base materialand at-least-one filler material allows the base material and theat-least-one filler material to be chosen with a different hardness,stiffness, lubricity, dynamic coefficient of friction, heat transfercoefficient, abradability, heat deflection temperature, glass transitiontemperature and/or melt temperature to improve the wearability of thetissue pad, which is important when high clamping forces are employedbecause tissue pads wear faster at higher clamping forces than at lowerclamping forces. Applicants found, in one experiment, that a 15%graphite-filled polytetrafluoroethylene tissue pad showed substantiallythe same wear with a 7 pound clamping force as a 100%polytetrafluoroethylene tissue pad showed with a 1.5 pound clampingforce. Having a flexible clamping arm and/or a flexible tissue padshould also improve the wearability of the tissue pad due to the abilityof the flexible member to more evenly distribute the load across theentire surface of the tissue pad. Further benefits and expressions ofthis embodiment are disclosed in U.S. provisional patent application,Ser. No. 60/548,301, filed on Feb. 27, 2004 and commonly assigned to theassignee of the present application, and which the entire contents areincorporated by reference herein.

In a fifth expression of the current embodiment, a tissue pad with abase material and at least two filler materials allows the base materialand the at-least-two filler materials to be chosen with a differenthardness, stiffness, lubricity, dynamic coefficient of friction, heattransfer coefficient, abradability, heat deflection temperature, and/ormelt temperature to improve the wearability of the tissue pad, which isimportant when high clamping forces are employed because tissue padswear faster at higher clamping forces than at lower clamping forces.Applicants found, in one experiment, that a 15% graphite-filled, 30%PTFE-filled polyimide tissue pad showed substantially the same or betterwear with a 4.5 pound clamping force as a 100% polytetrafluoroethylenetissue pad showed with a 1.5 pound clamping force. The advantage of a15% graphite-filled, 30% PTFE-filled polyimide tissue pad is increasedheat resistance, which improves the overall wear resistance of thetissue pad. This polyimide-composite clamp pad has a useful heatresistance up about 800° F. to about 1200° F., as compared to a usefulheat resistance up to about 660° F. of a PTFE clamp pad. Alternatively,Other materials are also useful for a portion of the tissue pad (that iselement 58 b′), such as ceramics, metals, glasses and graphite.

Referring to FIGS. 3a-e , one expression of clamp arm 56 has differentshaped slots for accepting two or more tissue pads. This configurationprevents mis-loading of the tissue pads and assures that the appropriatepad is loaded at the correct location within clamp arm 56. For exampleclamp arm 56 may comprise a distal T-shaped slot 53 a for accepting aT-shaped flange 53 b′ of distal clamp pad 58 a′ and a proximalwedged-shaped or dove tailed-shaped slot 55 a for accepting awedge-shaped flange 55 b′ of proximal clamp pad 58 b′. Tab stop 51engages the proximal end of proximal clamp pad 58 b′ to secure the clamppads onto clamp arm 56. As would be appreciated by those skilled in theart, flanges 53 b′ and 55 b′ and corresponding slots 53 a and 55 a mayhave alternate shapes and sizes to secure the clamp pads to the clamparm. The illustrated flange configurations shown are exemplary only andaccommodate the particular clamp pad material of one embodiment, but theparticular size and shape of the flange may vary, including, but notlimited to, flanges of the same size and shape. For unitary tissue pads,the flange may be of one configuration. Further, other tab stops arepossible and may include any of the multiple methods of mechanicallyattaching the clamp pads to the clamp arm, such as rivets, glue, pressfit or any other fastening means well know to the artisan.

In a second expression of the current embodiment, clamp pads 58 a and 58b are cut on a bias so the interface between the two pads creates anoverlap to minimize gapping (FIGS. 4a, 4b ). For example, a 45 degreebiased cut does allow some gapping to occur, but the amount of gap seenby the tissue is minimized.

In a third expression of the current embodiment, clamp arm 56 increasesin its height dimension from the distal end to the proximal end (D1<D2).Preferably, D2 is from about 105% to about 120% greater than D1 and morepreferably, D2 is from about 108% to about 113% greater than D1, andmost preferably, D2 is about 110% greater than D1. Slot 153 accepts theflanges from one clamp pad 58 or two clamp pads 58 a and 58 b. Taperedclamp arm 56 allows for the use of use flat pads and increases thepressure in the proximal portion of end effector 81 as well as theinterference with blade 79. When clamp arm 56 deflects at a greater ratethan the blade 79, pressure still exists at the tissue pad and bladeinterface and no gap is created. Additionally, the increased pressurehelps to offset the decreased blade amplitude at the proximal end ofblade 79 and provides a relatively constant pressure between the clamppad 58 and blade 79.

A first expression for a method for inserting clamp pads includes a)inserting first and second clamp pads having a first-shaped flange intoa clamp arm 56 having a slot that accepts the first-shaped flange; andb) engaging a pad stop to secure the clamp pads within the clamp arm. Ina second expression of this method one clamp pad may be fabricated froma polymeric material such as TEFLON, and the second clamp pad may befabricated from a base material and at least one filler material, whichis a different material from the base material and that clamp arm isfabricated from metal, such as stainless steel, or titanium. The tissuesurfaces of the clamp pads may be smooth or have tissue grippingfeatures, such as a saw-tooth configuration.

A third expression for a method for inserting clamp pads includes a)inserting a first clamp pad having a first-shaped flange into a clamparm having a slot that accepts the first-shaped flange; b) inserting asecond clamp pad having a second-shaped flange into the clamp arm havinga slot that accepts the second-shaped flange; and c) engaging a pad stopto secure the clamp pads within the clamp arm. In a fourth expression ofthis method one clamp pad may be fabricated from a polymeric materialsuch as TEFLON, and the second clamp pad may be fabricated from a basematerial and at least one filler material, which is a different materialfrom the base material and that clamp arm is fabricated from metal, suchas stainless steel, or titanium. The tissue surfaces of the clamp padsmay be smooth or have tissue-gripping features, such as a saw-toothconfiguration.

A first expression of a method for replacing clamp pads 58 would includethe steps of: a) disengaging a pad stop; b) removing a first clamp padfrom the clamp arm; c) removing a second clamp pad from the clamp arm;d) inserting third and fourth clamp pads into the clamp arm; and e)engaging a pad stop to secure the third and fourth clamp pads within theclamp arm. In a second expression of this method one of the third andfourth clamp pads may be fabricated from a polymeric material such asTEFLON, and the other clamp pad may be fabricated from a base materialand at least one filler material, which is a different material from thebase material and that clamp arm is fabricated from metal, such asstainless steel, or titanium. The tissue surfaces of the clamp pads maybe smooth or have tissue gripping features, such as a saw-toothconfiguration.

Referring now to FIG. 4, pivotal movement of the clamp member 60 withrespect to blade 79 is affected by the provision of a pair of pivotpoints on the clamp arm 56 that interface with the outer tube 72 andinner tube 76 respectively. The outer tube 72 is grounded to handle 68through rotation knob 29. Clamp arm 56 is pivotally connected to outertube 72 via corresponding through holes 52 a and 52 b on clamp arm 56and 52 c and 52 d on outer tube 72. A securing pin or rivet 57 slidesthrough holes 52 a-d to secure clamp arm 56 to outer tube 72. In oneembodiment pin 57 is laser welded to clamp arm 56 so that pin 57 isfixed to clamp arm 56 and rotates relative to outer sheath 72.

Inner tube 76 translates along the longitudinal axis of outer tube 72and is grounded to the handle 68 through rotation knob 29. Pivot studs54 a,b (54 a not shown) on clamp arm 56 engage pivot holes 54 c,d (54 dnot shown) at the distal end of inner tube 76. The pivotal connection ofclamp arm 56 to the inner and outer tubes 76, 72 provide more robustnessto the end effector 81 and minimize failure modes due to excessive axialor torsional abuse loads. Further, the embodiment increases theeffectiveness of the end effector 81 to provide clamp forces in excessof 1.5 lbs. Reciprocal movement of the actuating member 76, relative tothe outer sheath 72 and the waveguide 80, thereby affects pivotalmovement of the clamp arm 56 relative to the end-blade 79.

FIG. 4c illustrates a force diagram and the relationship between theactuation force FA (provided by actuation member 76) and transectionforce FT (measured at the midpoint of the optimal tissue treatmentarea).

FT=FA(X2/X1)  Equation [1]

Where FA equals the spring preload of proximal spring 94 (lessfrictional losses), which, in one embodiment, is about 12.5 pounds, andFT equals about 4.5 pounds as shown in FIG. 16c . FIG. 16c provides agraphical illustration of FT and FA as a function of trigger 34 movementas well as input forces at trigger 34.

FT is measured in the region of the clamp arm/blade interface whereoptimal tissue treatment occurs as defined by tissue marks 61 a and 61b. Tissue marks 61 a, b are etched or raised on clamp arm 56 to providea visible mark to the surgeon so the surgeon has a clear indication ofthe optimal tissue treatment area. Tissue marks 61 a, b are about 7 mmapart in distance, and more preferably 5 mm apart in distance.

Rotation of the transmission assembly 71 of ultrasonic surgicalinstrument 100 may be affected together with relative rotationalmovement of ultrasonic transducer 50 with respect to instrument handleassembly 68. In order to join the transmission assembly 71 to theultrasonic transducer 50 in ultrasonic-transmitting relationship, theproximal portion of the outer sheath 72 may be provided with a pair ofwrench flats 46. The wrench flats 46 allow torque to be applied by asuitable torque wrench or the like to thereby permit the waveguide 80 tobe joined to the ultrasonic transducer 50. The ultrasonic transducer 50,as well as the transmission assembly 71, is thus rotatable, as a unit,by suitable manipulation of rotation knob 29, relative to handleassembly 68 of the instrument. The interior of handle assembly 68 isdimensioned to accommodate such relative rotation of the ultrasonictransducer 50. A spring 28 is loaded against rotation knob 29 and aninner housing surface 65. Spring 28 provides a compression or forceagainst rotation knob 29 to inhibit inadvertent rotation of end effector81.

Referring now to FIGS. 2, 5, 6 and 16, force limiting mechanism 91provides a first and second compression spring, distal spring 96 andproximal spring 94. Distal spring 96 is operationally coupled to yoke33, which in turn is driven by trigger 34. Proximal spring 94 is inoperational relationship with distal spring 96. Distal spring 96generates the end effector load and proximal spring 94 maintains theconsistency of the end effector load. As a result, the end effector loadis more tightly controlled and component abuse load conditions arereduced. Washers 97 and 95 are a safe guard against distal spring 96being fully compressed (FIG. 5), thereby preventing the spring materialto yield and render spring 96 useless in subsequent clamp arm closures.As would be appreciated by one skilled in the art, the application of adual spring force limiting system has applicability in otherenergy-based surgical devices (such as RF, microwave and laser) thatencounter clamping forces, as well as mechanical devices, such as, clipappliers, graspers and staplers.

In one expression of the current embodiment, distal spring 96 has aspring constant greater than 100 pounds per inch and preferably greaterthan 125 pounds per inch and most preferably about 135 pounds per inch.It is not required that distal spring 96 be preloaded, but may bepreloaded at less than 10 pounds, and preferably less than 5 pounds, andmost preferably at about 1 pound. Proximal spring 94 has a springconstant greater than 25 pounds per inch and preferably greater than 50pounds per inch and most preferably about 70 pounds per inch. Proximalspring 94 is preloaded to a force necessary to achieve the desiredtransection force as noted in Equation 1, above, and is a function ofthe mechanical advantage of the clamp arm 56 coupling means andfrictional losses in the device. In a second expression of the currentembodiment, proximal spring 94 is preloaded at about 12.5 pounds.

Referring now to FIG. 16a , curve 82 illustrates actuation member 76force and curve 83 represents trigger 34 force as a function of theangular rotation of trigger 34 (on the x-axis, −18.0 is the clamp arm 56fully open and 0.0 is the clamp arm fully closed and against blade 79)under no tissue or minimal tissue load operation. Point 82 a representsthe point at which yoke 33 begins to deflect or compress distal spring96 and the actuation member 76 force increases as trigger 34 isdepressed further until the force reaches the preload value of proximalspring 94 at inflection point 82 b, and the slope of the force curvedecreases.

In FIG. 16b , curve 84 illustrates actuation member 76 force and curve85 represents trigger 34 force as a function of the angular rotation oftrigger 34 under abusive tissue load operation, whereby tissuecompletely fills the end effector in the open position. Point 84 arepresents the point at which yoke 33 begins to deflect or compressdistal spring 96 and the actuation member 76 force increases as trigger34 is depressed until the force reaches the preload value of proximalspring 94 at inflection point 84 b, at which point the slope of theforce curve decreases.

Referring now to FIGS. 2 and 5, surgical instrument 100 further providesfor a means for indicating to the surgeon that the trigger has reachedfull travel and the clamp arm 56 is applying the correct coaptationforce to the tissue. This is useful during protracted surgicaloperations or tissue transection activities when the surgeon's grip mayrelax, just a bit, without the surgeon's knowledge, and the pressuredelivered to the tissue from the clamp arm 56 may be unknowinglydecreased.

In one expression of the current embodiment, a detent spring 110 issupported within a detent support 112 located within housing portion 69.A detent tab 114 on trigger 34 engages and snaps back detent spring 110when trigger 34 is fully closed or actuation member 76 has reached itmost proximal travel. Detent spring 110 is generally planar and made ofa flexible plastic that adequately deflects when it engages tab 114thereby providing an audible and/or tactile signal to the surgeon thatthere is full end effector 81 closure. Advantageously, tab 114 strikesand deflects detent spring 110 when trigger 34 is rotated from the fullclosure position and in the opposite direction thereby providing anaudible and/or tactile signal to the surgeon that full closure of endeffector 81 no longer exists. As would be appreciated by the skilledartisan, the indicating means may be either tactile, audible or visualor a combination. Various types of indicators may be used including domeswitches, solid stops, cantilever springs or any number of mechanical orelectrical switches known to those skilled in the art. Further variousmeans may be used to provide feedback to the surgeon, including, but notlimited to, lights, buzzers, and vibratory elements.

Referring now to FIGS. 1, 2 and 6-8 housing 68 includes a proximal end,a distal end, and a cavity 59 extending longitudinally therein. Cavity59 is configured to accept a switch assembly 300 and the transducerassembly 50, which interfaces with housing 68 via switch assembly 300.

Transducer 50 includes a first conductive ring 400 and a secondconductive ring 410 which are securely disposed within the transducerbody 50. In one expression of the current embodiment, first conductivering 400 comprises a ring member, which is disposed between thetransducer 50 and the horn 130. Preferably the first conductive ring 400is formed adjacent to or as part of the flange member 160 within thecavity 162 and is electrically isolated from other electricalcomponents. The first conductive ring 400 is anchored to and extendsupwardly from a non-conductive platform or the like (not shown) which isformed within the transducer body 50. The first conductive ring 400 iselectrically connected to the cable 22 (FIG. 1) by means of one or moreelectrical wires (not shown), which extend along the length of thetransducer body 50 to the first conductive ring 400.

The second conductive ring 410 of the transducer 50 similarly comprisesa ring member that is disposed between the transducer body 150 and thehorn 130. The second conductive ring 410 is disposed between the firstconductive ring 400 and the horn 130 and therefore the first and secondconductive rings 400, 410 are concentric members. The second conductivering 410 is likewise electrically isolated from the first conductivering 400 and other electrical components contained within the transducer50. Similar to the first conductive ring 400, the second conductive ring410 preferably is anchored to and extends upwardly from thenon-conductive platform. It will be understood that the first and secondconductive rings 400, 410 are sufficiently spaced from one another sothat they are electrically isolated from each other. This may beaccomplished by using one or more spacers 413 disposed between the firstand second conductive rings 400, 410 or between the rings 400, 410 andother members within the transducer 50. The second conductive ring 410is also electrically connected to the cable 22 (FIG. 1) by means of onemore electrical wires (not shown), which extend along the length of thetransducer 50 to the second conductive ring 410. The second conductivering 410 is thus provided to partially define a second electricalpathway from the cable 22 to the switch mechanism 300. A suitableultrasonic transducer 50 is Model No. HP054, sold by EthiconEndo-Surgery, Inc. of Cincinnati, Ohio.

In one expression of the current embodiment, the distal end oftransducer 50 threadedly attaches to the proximal end of transmissionrod 80. The distal end of transducer 50 also interfaces with switchassembly 300 to provide the surgeon with finger-activated controls onsurgical instrument 100.

Switch assembly 300 comprises a pushbutton assembly 310, a flex circuitassembly 330, a switch housing 350, a first spring slip ring conductor360 and a second spring slip ring conductor 370. Switch housing 350 isgenerally cylindrical and is supported within handle assembly 68 by wayof corresponding supporting mounts on switch assembly 350 and housingportions 69 and 70. Housing 350 defines a first cavity 353, a mountingboss 352 and a second cavity 351. Cavity 353 is sized to accept theproximal end of transducer 50, whereby horn 130 passes through cavity351 to interface with transmission rod 80. Mounting boss 352 acceptsslip ring conductors 360 and 370, which in turn electrically engage ringcontacts 400 and 410, respectively. An alignment pin 354 and snap-fitpin 355 align with corresponding apertures of the flex circuit assembly330 and pushbutton assembly 310 to secure all components together asdiscussed below.

With particular reference now to FIG. 8a , slip ring conductors 360 and370 are generally open-ended O-shaped springs that slip onto mountingboss 352. Each spring slip-ring comprises two pressure point contacts(361 a-b and 371 a-b) that contact the respective ring conductor 400 and410 of transducer 50. The spring tension of the slip rings 360 and 370cause positive contact between contacts 361 a-b, 371 a-b and conductors400 and 410. It is evident that the slip-ring construction allowselectrical contact to be made even as transducer 50 may be rotated bythe surgeon during use of the instrument. Posts 364 and 374 of therespective slip rings electrically connect to the respective conductorwithin flex circuit 330 to complete the electrical circuit as shown inFIG. 8 c.

A flex circuit 330 provides for the electro-mechanical interface betweenpushbuttons 311 a, b, 312 a, b and the generator 30 via transducer 50.Flex circuit comprises four dome switches 332 a,b and 334 a, b that aremechanically actuated by depressing pushbuttons 311 a, b or 312 a, b,respectively of corresponding pushbutton assembly 310. Dome switches 332and 334 are electrical contact switches, that when depressed provide anelectrical signal to generator 30 as shown by the electrical wiringschematic of FIG. 8c . Flex circuit 330 also comprises two diodes withina diode package 336, also illustrated in FIG. 8c . Flex circuit 330provides conductors, 335 and 337 as is known to those in the art, thatconnect to slip ring conductors 360 and 370 via electrical tabs 364 and374, respectively, which in turn provide electrical contact to ringconductors 400 and 410, which in turn are connected to conductors incable 22 that connect to generator 30. Tabs 364 and 374 are soldered toconductors 335 and 337.

Flex circuit 330 generally wraps around switch housing 350 so that domeswitches 334 a, b and 332 a, b interface with the corresponding backingsurfaces 356 a, b and 358 a, b on switch housing 350. Backing surfacesprovide a firm support for the dome switches during operation, discussedbelow. Dome switches 334 a, b and 332 a, b may be fixedly attached tobacking surfaces 356 a, b and 358 a, b by any convenient method, suchas, an adhesive. Flex circuit is secured to switch housing 350 viaalignment pin 354 and snap-fit pin 355 on switch assembly 350 andcorresponding alignment hole 338 and snap-fit hole 339 on flex circuit330.

Layered on top of flex circuit is pushbutton assembly 310, which has acorresponding saddle-shape as flex circuit 330, and generally wrapsaround switch housing 350. Pushbutton assembly 310 comprises fourpushbuttons, distal pushbuttons 312 a, b and proximal pushbuttons 311 a,b which have corresponding pressure studs 315 a, b and 314 a, b. Thepushbuttons are connected to cantilever elements 313 a, b and 316 a, b,which provide a spring-back action after the pushbuttons are depressed.As is readily apparent, by depressing pushbuttons 311 and 312 thecorresponding pressure studs 314 and 315 depress against correspondingdome switches 334 and 332 to activate the circuit illustrated in FIG. 8c. Switches 312 a and b are in parallel so that a surgeon may operate thepushbuttons using either a left hand or a right hand. Likewise, switches311 a and b are in parallel so that a surgeon may operate thepushbuttons using either a left hand or a right hand. When the surgeondepresses either switch 312 a or 312 b, the generator will respond witha certain energy level, such as a maximum (“max”) power setting; whenthe surgeon depresses either switch 311 a or 311 b, the generator willrespond with a certain energy level, such as a minimum (“min”) powersetting, which conforms to accepted industry practice for pushbuttonlocation and the corresponding power setting.

Alternatively, the pushbuttons may be molded into the switch housing 350or into the handle assembly 68 to reduce the number of components andincrease the reliability of the overall device. The pushbuttons may beattached through small cantilever sections, which allow for sturdyattachment of the pushbutton to the other components, while at the sametime allowing for a low force to activate the pushbuttons.

Referring now to FIGS. 12-15, one expression of the current embodimentallows switches 311 a, b and 312 a, b configured in such a way toprovide an ergonomically pleasing grip and operation for the surgeon.Switches may be placed in the range of the natural swing of thesurgeon's thumb, whether gripping surgical instrument 100 right-handedor left handed. In a second expression of the current embodiment, theswitches are placed on housing 68 to prevent inadvertent buttonactivation on the side of the instrument opposite the thumb while thesurgeon depresses trigger 34 or rotates rotation knob 29. In a thirdexpression of the current embodiment a series of partitions, such asridges and/or depressions or “peaks and valleys” that are integratedonto the housing 68. In one example the housing defines a first surfaceand the series of partitions define at least one second surface suchthat the second surface is higher than the housing surface. Thepartition may also define a third surface that is lower than the housingsurface. As can be seen in FIGS. 1, 2 switches 312 a, b are surroundedby an upper ridge 320 and a lower ridge 324. Ridges 320 and 324 may bediscrete physical features, both separated from each other, or ridges320 and 324 may be continuous in nature without departing from the scopeof the invention. Further, the ridges 320 and 324 may continue acrossthe entire upper portion of housing 68, as shown in FIGS. 12-15, orridges 320 and 324 may be more discrete as shown in FIGS. 1 and 2. Thisconstruction and situation of switches 312 a, b prevent the risk ofinadvertent button activation even if a finger crosses over the buttondue to the fact that the ridges cause the finger to pass above the planeof the button. The ridges also provide tactile feedback to the surgeonas to the location of the pushbuttons and whether the button representsmin or max power activation. As is readily evident, switches 312 a, bare surrounded by ridges 320 and 324 and pushbuttons 311 a,b aresituated above and proximal of ridge 320. Such tactile feedback isessential to the surgeon, so the surgeon may continuously assess thesurgical site, but confidently understand which pushbuttons are beingactivated. In a further expression of the current embodiment, switch 312a, b are nestled within a depression 322 and further surrounded byridges 320 and 324.

Referring to FIG. 12, a surgeon's left hand is accessing instrument 100.The fore finger and middle finger are poised to activate trigger 34, andthe ring finger and pinkie grasp hand grip 39. The thumb is convenientlypositioned to sweep upward to activate pushbutton 312 a or 311 a. Ridges320 and 324 extend across the upper portion of housing 69.

In FIG. 13, the opposite side of instrument 100 shown in FIG. 12 isillustrated showing pushbuttons 311 b and 312 b. Here the surgeon'sforefinger is accessing rotation knob 29 to rotate end effector 81. Ascan be seen, pushbutton 312 b is subject to inadvertent activation bythe forefinger. However, ridge 324 causes the forefinger to elevateabove the plane of pushbutton 312 b thereby reducing the risk ofinadvertent activation.

In FIG. 14, the surgeon has depressed trigger 34 to close clamp arm 56against blade 79, and the left thumb has easily accessed pushbutton 312b to activate max power.

In FIG. 15, the surgeon has depressed trigger 34 to close clamp arm 56against blade 79, and the left thumb has easily accessed pushbutton 311b to activate min power.

Referring to FIG. 17, an expression of surgical instrument 100 is showngraphically illustrating a surgeon's finger placement on instrument 100.Instrumental in the activation of the instrument 100 is the placement ofthe forefinger 382 and middle finger 384 on trigger 34. (Using theforefinger and middle finger to activate trigger 34 is exemplary only.Surgeons with smaller hands may opt to activate trigger 34 with themiddle finger and ring finger, thereby making the forefinger availableto rotate knob 29 or even use the ring finger and pinkie to activetrigger 34.) Trigger 34 comprises a base element 45, which comprises thedetent tab 114 and linkage with yoke 33, discussed below. Attached tobase element 45 is a generally T-shaped finger interface 43, which inconjunction with base element 45 define two generally U-shaped openings,a forefinger groove 42 and a middle finger groove 44. The most distalsurface portion of T-shaped finger interface 43 defines an actuatingsurface 41 that also accepts placement of fingers 382 and 384. Grooves42 and 44 are sized to accept different sized fingers, a common variableas is evident depending upon the sex and size of the surgeon. In a firstexpression of the current embodiment, the size of grooves 42 and 44 arebased on anthropic data for 5th percentile females through to 95thpercentile males for finger size. In a second expression of the currentembodiment, grooves 42 and 44 are tapered, whereby the dimension of eachgroove opening is larger than the dimension of base of each groove 42and 44. This configuration advantageously allows fingers of varying sizeto nestle snuggly within each groove and minimize the clearance betweenthe finger and walls of the grooves.

Referring now also to FIGS. 10 and 11, the clamp arm 56 is fully openrelative to the blade 79 when trigger 34 is in its most distal position(FIG. 10). Fingers 382 and 384 may be placed within respective grooves42 and 44 or alternatively on surface 41 to actuate trigger 34 throughits arcuate travel designated by arrow 47. When trigger reaches its fullproximal travel (when detent tab 114 engages detent spring 110), theclamp arm 56 is in its fully closed position relative to the blade 79(FIG. 11). In order to reverse the trigger along its travel 47, fingers382 and 384 engage grooves 42 and 44 and push trigger 34 distally toopen the end effector. The clamp arm 56 is not biased open so thesurgeon cannot control the opening of clamp arm 56 via surface 41.

Referring now to FIG. 18, elements having similar reference numerals asshown in FIG. 2 have the similar function as already discussed.Particular attention is directed to an alternate handle assembly 168 foractuating the end effector 81. The handle assembly 168 includes twopivoting handle portions 420 and 422 coupled to a right shroud 169 and aleft shroud 170.

The right shroud 169 is adapted to snap fit on the left shroud 170 via aplurality of inwardly facing prongs formed on the left shroud 170 toform housing 171. When the left shroud 170 is attached to the rightshroud 169, a cavity is formed therebetween to accommodate variouscomponents that form the handle assembly 168 as further discussed below.Apertures 172 and 174 are also formed to accommodate thumb ring orhandle portion 420 and finger ring or handle portion 422, which arelocated exterior of the left and right shrouds to the actuating linkagecontained within the left and right shrouds. Aperture 173 is also formedat the proximal end of shrouds to accommodate transducer 50 (See FIG. 8b).

Handle assembly 168 includes a U-shaped yoke 424 slidably attachablewithin housings 169 and 170 via slots 421 a and 421 b and pins 423 a and423 b, respectively. The distal end of handle 420 at hole 402 attachesto right shroud 169 and yoke via pin 423 a, and the proximal end ofhandle 420 attaches to yoke 424 via link 428 attached to hole 404 viapin 426 and hole 410 via pin 430. The distal end of handle 422 at hole406 attaches to right shroud 169 and yoke via pin 423 b, and theproximal end of handle 422 attaches to yoke 424 via link 432 attached tohole 408 via pin 434 and hole 412 via pin 430. In practice as thehandles 420 and 422 are moved away from housing 171 (for example, thesurgeon's thumb cooperates with handle 420, and the surgeon's forefingerand middle finger cooperate with handle 422), end effector 81 moves awayfrom blade 79 to form an open jaw (the open position), and as handles420 and 422 are moved toward housing 171, end effector 81 rotates towardblade 79 to capture tissue (the closed position).

In one expression of the current embodiment, a detent spring 482 issupported within housing portion 171. A detent cam 480 rotates on yoke168 and engages and snaps back detent spring 482 when handles 420 and422 are in the fully closed position. Detent spring 482 is generallymade of a flexible plastic that adequately deflects when it engages cam480 thereby providing an audible signal to the surgeon that there isfull end effector 81 closure. Advantageously, 480 strikes and deflectsdetent spring 482 when handles 420 and 422 are rotated from the fullclosure position and in the opposite direction thereby providing anaudible signal to the surgeon that full closure of end effector 81 nolonger exists.

Referring also now to FIG. 24, a second expression of the currentembodiment is shown having an actuator post 433 attaches to handle 422and engages a dome switch 435 covered by silicon rubber located onhousing assembly 171. When handle 422 is fully closed, post 433 pressesagainst the silicone which in turn transfers the force to the domeswitch 435, allowing the switch to provide an audible and tactilefeedback to the surgeon. In one embodiment post 433 is a cylinder havinga diameter of 0.170 inches with a 0.070 inch slot in the middle. Apreferred durometer for the silicon rubber material is 20 Shore A.

Referring also now to FIG. 23, also enclosed within housing 171 areconnector 450, slip rings 452, 454, flex circuit 456 and rocker switch462. Rocker switch 462 rotatably attaches to right shroud 169 viaaperture 469 and switches 462 and 464 are positioned exterior housing171 for access by the surgeon. Switches 462 and 464 are mechanicallyconnected via a rocker arm 466 comprising a pivot post 468 whichinterfaces with aperture 469. In this configuration, switches 462 and464 cannot be simultaneously depressed, which, if were the case, wouldprovide an error message from generator 30. A flex circuit 456 providesfor the electro-mechanical interface between switches 464 and 466 andthe generator 30 via the transducer 50 (see FIG. 8b ). Referring to FIG.21, flex circuit 456 includes, at the distal end, two dome switches 500and 502 that are mechanically actuated by depressing correspondingswitches 464 and 466, respectively. Dome switches 500 and 502 areelectrical contact switches, that when depressed provide an electricalsignal to generator 30 as shown by the electrical wiring schematic ofFIG. 22. Flex circuit 456 also comprises two diodes within a diodepackage 504, also illustrated in FIG. 22. Flex circuit 456 providesconductors, as is known to those in the art, that connect to slip ringconductors 452 and 454 via connector 450, which in turn provideelectrical contact to ring conductors 400 and 410 (FIG. 8b ), which inturn are connected to conductors in cable 32 that connect to generator30.

With particular reference now to FIGS. 19 and 20 a-b, slip ringconductors 452 and 454 are generally open-ended O-shaped springs thatslip onto mounting surfaces 453 and 455 of connector 450, respectively.Each spring slip-ring comprises two pressure point contacts (510 a-b and522 a-b) that contact the respective ring conductor 400 and 410 ofhandpiece 50. The spring tension of the slip rings 452 and 454 causepositive contact between contacts 510 a-b, 522 a-b and conductors 400and 410. It is evident that the slip-ring construction allows electricalcontact to be made even as hand piece 50 may be rotated by the surgeonduring use of the instrument. Posts 512 and 524 of the respective sliprings electrically connect to the respective conductor within flexcircuit 456 to complete the electrical circuit as shown in FIG. 22.

Referring again to FIG. 18, rotation coupler 130 rotatably engages thedistal end of right and left shrouds 169 and 170. Rotation knob 129couples to rotational coupler 130, whereby two spring tabs 175 and 175 a(not shown) provide an outward tension or force against the innersurface of rotation knob 129 to inhibit inadvertent rotation of endeffector 81.

In an alternate expression of the invention, handles 420 and 422 have asoft-touch molded thermo plastic elastomer liner 550 on the innersurface of handles 420 and 422. Plastic liner 550 provides comfort tothe surgeon and prevents finger and hand fatigue. Plastic liner 550 alsoprovides an enhance gripping surface between the handles and thesurgeon's thumb and fingers as opposed to the smooth plastic surfaceinterface of the prior art. This is particularly advantageous foraccepting multiple digit sizes of male and female surgeons and stillproviding a comfortable and positive gripping surface. Plastic liner 550may be smooth or have contours molded onto the surface of liner 550,such as ribs, as illustrated in FIGS. 23 and 24. Other contours may bebumps, and peaks and valleys. Various other shapes and interfaces arewithin the scope of this invention as would be obvious to one skilled inthe art. Plastic liner 550 is also useful on the interface between thesurgeon's finger and trigger 34 (FIG. 12).

In one expression of the current embodiment, the soft-touch liner 550has a durometer (hardness) rating from about 35 Shore A to about 75Shore A, and more particularly from about 50 Shore A to about 60 ShoreA. Such appropriate materials are available from LNP of Exton, Pa.(stock no. 8211-55 B100 GYO-826-3) and Advanced Elastomer Systems ofAkron, Ohio (stock no. 8211-55B100).

The soft-touch material may also be useful to help the surgeon identifya particular feature of the instrument while the surgeon is focused onthe operation at hand. For example, a “soft touch” having one contourinterface may be placed on the “max” button, and a “soft touch” having asecond contour interface may be place on the “min” button so the surgeonmay easily recognize the presence of either button without having tolose focus of the surgical site. “Soft touch” may also be implemented onknobs 29 and 129 with contours to identify various rotation positions ofend effector 81.

While the present invention has been illustrated by description ofseveral embodiments, it is not the intention of the applicant torestrict or limit the spirit and scope of the appended claims to suchdetail. Numerous variations, changes, and substitutions will occur tothose skilled in the art without departing from the scope of theinvention. Moreover, the structure of each element associated with thepresent invention can be alternatively described as a means forproviding the function performed by the element. Accordingly, it isintended that the invention be limited only by the spirit and scope ofthe appended claims.

We claim:
 1. An ultrasonic clamp coagulator apparatus comprising: ahousing comprising an actuator; an outer tube having a proximal endjoined to the housing, and a distal end; an ultrasonic waveguide havinga proximal end and a distal end and further positioned within the outertube; an ultrasonically actuated blade attached to the distal end of thewaveguide; a clamp member pivotable with respect to the blade forclamping multiple tissue types of varying thickness between the clampmember and the blade; and a force limiting mechanism comprising: a firstcompression spring having a first spring constant, positioned betweenthe actuator and the clamp arm wherein the first compression springtransfers a force at a first rate as a function of the motion of theactuator to pivotably move the clamp member toward the blade and; asecond compression spring having a second spring constant less than thefirst spring constant, wherein the second compression spring transfers aforce as a function of the tissue thickness positioned between the clampmember and the blade, and wherein at least one of the first and secondcompression springs is pre-compressed to provide a preload less than therespective spring constant.
 2. The ultrasonic clamp coagulator apparatusin accordance with claim 1, wherein the first compression spring has aspring constant greater than 100 pounds per inch.
 3. The ultrasonicclamp coagulator apparatus in accordance with claim 2, wherein the firstcompression spring has a spring constant greater than 125 pounds perinch.
 4. The ultrasonic clamp coagulator apparatus in accordance withclaim 3, wherein the first compression spring has a spring constant ofabout 135 pounds per inch.
 5. The ultrasonic clamp coagulator apparatusin accordance with claim 1, wherein the second compression spring has aspring constant greater than 25 pounds per inch.
 6. The ultrasonic clampcoagulator apparatus in accordance with claim 5, wherein the secondcompression spring has a spring constant greater than 50 pounds perinch.
 7. The ultrasonic clamp coagulator apparatus in accordance withclaim 1, wherein the second compression spring has a spring constant ofabout 70 pounds per inch.
 8. The ultrasonic clamp coagulator apparatusin accordance with claim 1, wherein the second compression spring ispreloaded to a value to provide a required transaction force.